RF Cables and Connectors

RF Cables and Connectors

The final word is on using RF cables and various connectors. As mentioned before, RF cables are one of the major sources of loss on wireless networks. Do not save money on cabling—get the lowest attenuation rating (estimated in dB loss per 100 feet at a given frequency) cables possible. Get cables with preinstalled connectors. Installing connectors yourself is possible, but the end result is likely to be less reliable than the industry standard. RF signal loss due to bad connectors or damaged cables can be enormous, yet hard to discover. Do not forget that the cable should have the same impedance (usually 50 Ohms) as the rest of your wireless components. Choose cable connectors that suit your client devices and existing antennas. You can connect anything with appropriate cheap barrel or crimp connectors, but just one such connector might bring an additional 2 to 3 dB loss, halving your transmission power and receiving sensitivity. When it comes to wireless hardware, pigtail connectors gave (and keep giving) us the biggest headache of all. In mobile site survey and security evaluation practices, pigtails quickly wear off, the connectors are easily broken, and you have to ensure that the MMCX connector does not slip off the client card (fixing it to the card or laptop with a sticky tape helps). The most common pigtails are Aironet-type, which also fit the majority of Prism chipset cards, and Lucent/Orinoco pigtails, which fit Hermes chipset cards. In our experience, the latter are of better quality and lock on a card in a more reliable way. Make sure you have spare pigtails so as not to be caught by a broken one in the middle of your security audit.

Remember, although cabling and connectors are not directly relevant to wireless security, it doesn't matter what side of wireless networking you are involved with, a strong, clear signal and good receiving sensitivity are essential. A WLAN with significant signal loss would have a very low resilience to jamming and Layer 1 man-in-the-middle attacks. This is yet another point that underlines the "network security and reliability from the initial design stages" concept.